Re: BBU Cache vs. spindles

On Oct 7, 2010, at 4:38 PM, Steve Crawford wrote:

> I'm weighing options for a new server. In addition to PostgreSQL, this machine will handle some modest Samba and
Rsyncload. 
>
> I will have enough RAM so the virtually all disk-read activity will be cached. The average PostgreSQL read activity
willbe modest - a mix of single-record and fairly large (reporting) result-sets. Writes will be modest as well but will
comein brief (1-5 second) bursts of individual inserts. The rate of insert requests will hit 100-200/second for those
briefbursts. 
>
> So...
>
> Am I likely to be better off putting $$$ toward battery-backup on the RAID or toward adding a second RAID-set and
splittingoff the WAL traffic? Or something else? 

A BBU is, what, $100 or so? Adding one seems a no-brainer to me. Dedicated WAL spindles are nice and all, but they're
stillspinning media. Raid card cache is waaaay faster, and while it's best at bursty writes, it sounds like bursty
writesare precisely what you have.